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How is cheese made?

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Quick answer

Cheese is made by adding starter bacteria and rennet to warm milk, which makes its casein proteins clump into a solid curd. The curd is cut and heated to release liquid whey, then drained, salted and pressed into shape. Many cheeses are then aged so microbes and enzymes develop flavour.

Cheese is made by curdling milk with rennet or acid so its casein proteins clump into curds, then draining off the liquid whey. The curds are cut, heated, salted, pressed and often aged, while bacteria and enzymes slowly develop each cheese's flavour and texture.

Step by step

  1. Milk is warmed and starter bacteria are added, which begin converting lactose into lactic acid.
  2. Rennet is stirred in, and its chymosin enzyme causes casein proteins to link into a firm gel.
  3. The gel is cut into cubes, then heated and stirred so the curds shrink and release whey.
  4. Whey is drained, and the curds are salted and packed into moulds or hoops.
  5. Moulds are pressed to remove more whey, giving the cheese its final shape and firmness.
  6. The cheese is aged in controlled cool, humid rooms while enzymes and microbes develop flavour.

Key things to understand

  1. Cheesemakers warm milk and add starter bacteria, which turn some lactose into lactic acid and begin acidifying the milk.
  2. Rennet, containing the enzyme chymosin, snips a protein on the surface of casein micelles so they bind together with calcium into a firm gel.
  3. The gel is cut into small cubes and often heated and stirred, which squeezes out whey and firms the curds.
  4. The drained curds are salted and pressed into moulds, where salt controls moisture and microbes and pressing sets the final shape.
  5. During ageing, enzymes and microbes break down proteins and fats over weeks to years, building flavour and changing texture.

Labelled diagram

  1. Milk and starter

    Warm milk receives bacteria that begin turning lactose into lactic acid.

  2. Rennet coagulation

    Chymosin makes casein proteins bond into a solid, jelly-like curd.

  3. Cutting curds

    Cubed, heated curds shrink and push out the watery whey.

  4. Salting and pressing

    Salt controls moisture and microbes; pressing sets shape and firmness.

  5. Ageing

    Enzymes and microbes break down proteins and fats, building flavour over time.

The main stages of making cheese

Real-world examples

  • Paneer, made across India by curdling hot milk with lemon juice and pressing the curds in muslin, is an unaged acid cheese.
  • Cheddar from England is made by stacking and turning slabs of curd, a step called cheddaring, before milling and pressing.
  • Parmigiano Reggiano wheels from northern Italy are aged for at least twelve months, developing crunchy crystals of amino acids.
  • Blue cheeses such as Roquefort are pierced with needles so air reaches Penicillium mould growing inside the paste.

Common mistake

✗ Myth: All cheese is made with rennet taken from calves' stomachs.

✓ Fact: Most cheese today is made with chymosin produced by fermentation with microbes or with fungal enzymes, and acid-set cheeses such as paneer use no rennet at all.

People also ask

How is cheese made step by step?
Milk is warmed and acidified with starter bacteria, then rennet is added so the proteins set into a gel. The gel is cut, heated and stirred to release whey, which is drained. The curds are salted, packed into moulds and pressed. Most cheeses are then ripened for weeks to years before eating.
What makes cheese different flavours?
Flavour depends on the milk, the bacterial cultures, any added moulds, how much whey is removed, the salt level and how long and where the cheese ages. During ripening, enzymes break proteins into savoury amino acids and fats into sharp fatty acids, so a young cheese tastes mild while an aged one tastes stronger.
Is cheese made from curd?
Cheese is made from curds, but not the same thing Indians call curd. Dahi is milk gelled by bacterial acid and eaten whole. Cheese curds come from milk set with rennet or acid, cut so the whey drains away, then salted, pressed and often aged into a far firmer, more concentrated food.
What is rennet and where does it come from?
Rennet is a set of enzymes, mainly chymosin, that curdles milk. It was traditionally taken from the stomach lining of young calves, but most cheese today uses chymosin made by fermentation with microbes or enzymes from fungi, which suits vegetarians.
How is paneer different from most cheeses?
Paneer is curdled with acid, such as lemon juice or vinegar, added to hot milk instead of rennet. It is pressed and eaten fresh without ageing, which is why it does not melt but softens when heated.
Why do some cheeses have holes?
In Swiss-type cheeses such as Emmental, propionic acid bacteria consume lactic acid during warm ripening and release carbon dioxide gas. The gas collects in bubbles within the firm paste, leaving the characteristic round eyes.
How much milk does it take to make cheese?
A hard cheese typically needs around ten litres of milk per kilogram, because most of the milk's water leaves as whey. Soft, moist cheeses keep more water and need less milk per kilogram.

Part of the guide: Food & Kitchen Science →